Refrigerator defrosting system



p 1952 w. L. HANSEN ETAL 2,612,026

' REFRIGERATOR DEFROSTING SYSTEM Filed NOV. 10, 1949 2 SHEETS-SHEET 1 //VV/V7'0P$ WILL/HM L. HANSEN HAREY' MANSON p T952 w. L. HANSEN ETAL 2,612,026

. REFRIGERATOR DEFROSTING SYSTEM Filed Nov. 10, 1949 2- SHEETS-SHEET 2 H6 3 7 T0 msnnosm To mgnuosmr I 26. I 26 To TIMER TO TIMER 32 28 T0 use 32 T0 use WILL/0M L HANSEN HARRY 6'. Mfl/VSON flTTOP/VEYS.

Patented Sept. 30, 1952 [ENTTOFFlCE SYSTEM:

WiIIiam L. Hansen and Harry G. MansongPrinceton, Ind., assignors to Hansen Manufacturing Company,.P rinoeton, Ind.,,a corporation of In- Application Novemberio, 194e, SerialNo. 126,634

" 6 Claims.

This invention relates to a defrosting system adapted to both domestic-and industrialrefrigerators. More particularly still, this invention relates to a refrigeration system including a de-v frosting unit, and to a cycle-of operation for maintaining a refrigerator defrosted. v

A refrigerator, either domestic or industrial, includes an evaporator, coils, or some other similarunit through which refrigerant is passed in order to chill the surface. of the .unit and thereby bring about an exchange of heat between theunit and the enclosure being refrigerators 'periodicallyto defrost the evaporator to,

remove the ice therefrom, and thus to restore it to efiicient operating conditions. Some refrigerators require that this operation be performed manually, while others are automatic and 'bring about the defrosting of the evaporator at intervals, say, once every twenty-four hours. In connection with the automatic defrosting arrangements, it is customary merely to inter- I rupt the operation of the compressor or refrigeration unit so that the evaporator will become warm, due to the lack of supply of refrigerant thereto and permit the ice gradually to melt 01f. Inasmuchas this normally requires some hours, even if carried out once a day, it is a disadvantage in that the refrigerator has a tendency to warm up throughout,'andthis is never a desirable occurrence, and sometimes cannot be permitted at all. I f

Furthermore, under these conditions, a continuous twenty-four hour period of operation of the refrigerator will cause suflicient accumulation of frost and ice on the evaporator or coils that the efficiency thereof is severely impaired.

The particular object of the present invention is to provide an arrangement whereby the evaporator or coils of a refrigerator is maintained sub-' stantially free of ice at all times.

Another object is to provide an arrangement in connection with a refrigerator .which maintains it at maximum operating efficiency at all times.

A still further object of this invention isto provide an automatic defrosting arrangement,

for a refrigerator which is inexpensive to construct and which can readily be applied to con ventional refrigerator structures.

A still further object is to provide an automaticdefrosting, arrangement which .is readily adaptable to any type of'refrigerator and re-' become more, apparent upon reference to the. followingdescription taken in connection with the accompanyingdrawings,v in which:

Figure 1 is a perspective view showing an evaporator of the type commonly employed in connection with domesticv refrigeratorsand including, adefrosting heater according to my invention;

Figure 2 is a diagrammatic. view. illustrating the wiring diagram associated with this invention;-

Figures 3 relation of the timer operated cams which control the switches of the control circuit of Figure 2; and

Figure5 is a perspective viewshowinga typical time arrangement for supplying the cams of Figures 3 and '4.

Referring tothe drawings, Figure 1, illustrates an evaporatorunit I0 .which it will be understood ism'erely exemplary of a number of differenttypes of "arrangements that could be "employed for providing .a refrigerated surface to effect. a heatexchange between the refrigerant and the .zone being refrigerated. The evaporator shown in Figure 1 is one type encountered in a number of conventional domestic -refrigerators.

Associated with evaporator [0, according to this invention,'i's aheater element l6 which is U preferably an electric unit so as to be readily controllable. The-'heatingelement I6 is shown as comprising a relatively thin member mounted on or integral with the side wall of evaporator Hi. It will be understood that a number of different manners of associating the evaporator ID and the heating element It could be employed. and that the essential thingis that the heating element it is so situatedthat, when it is energized, it will bring aboutmelting of thefrost and ice which accumulates on evaporator 10 during a refrigerating cycle thereof.

and 4 are views showing the cor- S! is in its second position.

It will also be understood that heating ele- -ment It could extend over whatever portion of the outer surface of evaporator I it was found desirable to heat, or that there could be a plurality of the elements 16, as, for example, one

i on each side of the evaporator.

According to this invention, the refrigeration unit and the heating element are alternately energized, so that at no time is there any substantial accumulation of ice or frost on the surface of the evaporator. One manner of controlling the energization of the refrigeration unit and heating element is illustrated in Figure 2.

In Figure 2 the drive motor for the refrigeration unit is indicated at l8, and it will be seen 'perature of the said enclosure reached a predeto be connected between the power lines LI and L2 in series with a switch S2 and thermostatic switch mechanism 20. Heating element [6 has one side thereof connected to line L2 and the other side thereof connected to a terminal 22 of switch S2.

In one position S2 establishes a circuit from line L! to thermostatic switch 20, and in its other position, it interrupts the circuit to the thermostatic switch and closes on contact 22 to bring about energization of heating element l6.

In order to provide for the alternate energization of drive motor I8 and heating element I6 according to a predetermined timed cycle, there is provided a timer motor 24 which has one side connected with power line L2 and its other side connected with a movable blade of a switch SI. SwitchSl has a first position where it closes on contact 26 that is connected with the drive motor side of thermostatic swtich 20. 'The said switch also has a second contact 28 that is connected with line Ll.

Switches S! and S2 are normally urged toward their second positions and are adapted for being moved toward their first said positions by cams mounted on the output shaft of the timer motor 24. These cam arrangements are shown in Figures 3 and 4.

Figure 3 shows that thereis a cam at 30 for controlling switch SI. The cam comprises the recess 32 which permits switch SI to rest in its second position for a predetermined length of time that cam 30 is rotated. Cam 30 comprises the raised part 34, and this portion of the cam holds, switch S! in its first position for a predetermined length of time.

The cam for controlling switch S2 is indicated at 36, and this cam also comprises a recess 38 and a raised part 40, the said recess being effective for permitting switch S2 to move to its second position with the raised part being effective for moving the said switch to its first position.

Thecams 30 and 36 are mounted on the drive shaft 42 of timer motor 34 and are fixedly oriented thereon to obtain a predetermined sequence of operation. Reference to Figures 3 and 4 will reveal that recess 32 has a greater cercumferential extent than recess 38, and that cams 30 and 36 are so aligned thatswitch S! is permitted to move into its secondposition where its blade closes on contact 28 prior to movement of S2 into position where its blade closes on contact 22.

Further, cam 36 moves s itch S2 out of enga ement with contact 22 prior t movement f switch SI out of en agement with contact 28. It ill be ap arent that the entire period of actuation of s itch S2 into its sec nd'nosit on takes place ith n the l m ts f the period that switch termined amount, a refrigeration cycle would be automatically initiated.

Element 20 could also comprise means responsive to the temperature at the surface of the evaporator, this arrangement commonly being employed in connection with domestic refrigerators.

In connection with a number of refrigeration systems, the refrigerator unit includes a compresser and receiver, and when the refrigeration unit operates, it compresses the refrigerating medium and delivers it in the form of a liquid to the receiver. Thereafter the liquid refrigerant is conveyed to the evaporator and admitted thereto under the control of a float valve or thermostatically controlled valve to cause chilling of the said evaporator.

With an arrangement of this nature the control of the drive motor 18 could comprise a pressure responsive element that initiated operation of the said unit when the supply of refrigerant in the receiver reached a predetermined minimum value, and interrupted operation of the said unit when the supply of refrigerant in the receiver again reached a predetermined value.

It will, accordingly, be understood that the element 20 is not to be considered as limited to a simple thermostatic switching element, but may comprise any suitable system for periodically initiating operation of the drivemotor of the refrigeration unit in response to a stimulus indicating the need for a supply of compressed refrigerant into the refrigerating system.

In operation, assuming the element 20 to be open so that drive motor 18 is de-energized, cams 30 and 36 will occupy substantially the positions in which they are illustrated in Figure 5. In these positions the cams hold switches Si and S2 in the positions in which they are illustrated in Figure 2. Inasmuch as element 20 is open, timer motor 24 is de-energized.

When element 20 closes, indicating the need for operation of the refrigeration unit to supply refrigerant to the system, timer motor 20 becomes energized simultaneously with drive motor 18. Timer motor 24 drives the cams in the direction indicated by the arrows thereon and commences to accumulate the maximum length of time that motor l8 will be energized.

After the elapse of a predetermined length of time from the time the timer and drive motor are energized, cam 3!] permits switch Si to close on contact 28, thus establishing a holding circuit for timer motor 24 that will retain it energized until switch SI is again moved into engagement with contact 26.

After switch SI has moved into engagement with contact 28, switch S2 is actuated by cam 36 to move into engagement with contact 22. This last-mentioned movement of switch S2 deenergizes drive motor 18, thereby halting operation of the refrigeration unit and energizing heating element 16 to initiate a defrosting cycle for the refrigerator.

After a predetermined timed period, determined by the arcuate extent of recess 38 of cam 36, switch 82' is returned to its original position, thereby jde-energizing'heating element I6 and again establishing the energizing circuit for drive motor'lB to element 20. Normally, element 20 will at this time be open and drive-motor [8 will not again become energized. V

Shortly .after switch S2 is returned to its original position by cam 36, cam 30 returns switch SI to its original position'in engagement with contact 36. At this time, inasmuch as element 20 is open, timer motor 24 will be deenergized and will halt in the position in which it started.

This completes a cycle of refrigeration and defrosting and leaves the evaporator free of frost and ice and in efficient condition for further refrigeration. At any time that element 20 again indicates the need of operation of the refrigeration unit, the above cycle will be repeated. The evaporator will therefore be maintained in a defrosted condition substantially all of the time.

It will be apparent that the timed period of operation of drive motor l8 may vary, and that it may be desirable to interrupt its operation at varying points during the said timed period, and under these circumstances, substantially the same cycle of operations may be obtained by merely lengthening recess 32 of cam 30 so as to be certain of establishing the holding circuit for the timer motor 24 prior to the lie-energization of drive motor [8. In any case there will be successive periods of operation of drive motor l8 and heating element Hi.

It will also be evident that it may at times and under certain circumstances be desirable first to operate heating element It, and thereafter to initiate operation of the refrigeration unit by energizing motor l8. This, of course, could readily be accomplished merely by interchanging the positions of drive motor l8 and heating element is in the circuit shown in Figure 2, with the provision of any suitable control means for the said motor in addition to the timer control thereof, if further desirable or necessary.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

We claim:

1. In a refrigeration system: a refrigeration unit having a drive motor, a defrosting heater, a switch having a first position for establishing a circuit through said drive motor and a second position for establishing a circuit through said heater, a thermostat in the circuit between said switch and motor responsive to a predetermined temperature in the zone being refrigerated to complete the circuit from the switch to the motor, a timer in parallel with said motor so as to be energized simultaneously therewith and having a cam operable after a predetermined period of energization of said timer to move said switch from its first to its second position for a predetermined timed period, and circuit control mechanism actuated by said timer operable automatically to maintain said timer energized during said timed period and to de-energize said timer at the expiration of said timed period.

2. In a refrigeration system; a refrigeration unit having a drive motor, a defrosting heater, a switch having a first position for establishing a tor, a timer in parallel with said motor so astobe energized simultaneously therewith and having a first cam operable after a predetermined period of energization of said timer in operable engagement with said switch to move it from its first to its second position for a timed period, and

means operable automatically to maintain said timer energized during said timed period, said means comprising a second switch connected to bypass said first-mentioned switch and thermostat, and a second timer cam in operable engagement with said second switch to move it into closed position prior to the initiation of said timed period and into open position after the expiration of said timed period.

3. In a refrigerator having a refrigeration unit, a drive motor for said unit, a defrosting heater, a timer and a thermostat, an electric circuit therefor, said thermostat being operative at a predetermined temperature in the enclosure being refrigerated to energize said motor and timer, and a circuit control mechanism actuated by said timer operable to de-energize said drive motor after a predetermined total period of time of energization thereof and to simultaneously enerize said heater.

4. In a refrigerator having a refrigeration unit, a drive motor for said unit, a defrosting heater, a timer and a thermostat, an electric control circuit therefor, said thermostat being operative at a predetermined temperature in the enclosure being refrigerated to energize said drive motor and timer, and a circuit control mechanism actuated by said timer operable to de-energize said drive motor after a predetermined total period of time of energization thereof, and to energize said heater for a predetermined time period, said' mechanism being thereafter operable to automatically de-energize said timer after the expiration of the predetermined period of energization of said heater.

5. In a refrigerator having a refrigeration unit, a drive motor therefor, a defrosting heater, a timer, and a thermostat, a control circuit therefor, said thermostat being operative at a predetermined temperature in the enclosure being refrigerated to energize said drive motor and timer, a switch having a first position wherein said drive motor is energized and a second position wherein said heater is energized, and a circuit control mechanism actuated by said timer operative after, a predetermined total time period of energization of said drive motor to move said switch into its second position and after a predetermined further total time period to return said switch to its first position, said mechanism being thereafter operable to automatically de-energize said timer after said switch has returned to its first position.

6. In a refrigerator having an evaporator, a refrigeration unit for supply refrigerant to said evaporator and including a drive motor, an electric circuit connected with said motor, an electric heater in said circuit mounted on said evaporator energizable to defrost the evaporator, a thermostat in said circuit operable to energize said drive motor in response to a predetermined temperature in the zone being refrigerated, a timer connected in said circuit to be energized simu1 taneously ,With sa1d:drive motor, and-a circuit control mechanism actuated-by said timer after a predetermined period of energization thereof to de energize said drive motor and energize said heater; fora, further predetermined period of time and thereafter to de-energize said heater and timer; 2

WILLIAM L; HANSEN. HARRY G. 'MANSONJT REFERE EsciTED V The following references are bf rec-0rd in-the fileE-of this patent:

Number 8 UNITED'STATES' PATENTS.

Name 2 Date- I Dob 1e June 13, 1933 Zurcher. 'Ndv. '10, 1936 Ka-gi July 13,1937, -SchaLa.f' Aug. 9, 1938 Newton June 10,1941 Newton Mar. 9,1943

Smithf Mar. 14,1950 

